I bought an Alpine unit a couple of years ago which had a Parrot made bluetooth handsfree built into it. This worked great as a handsfree calling solution, but the head unit wasn't capable of A2DP streaming, which always annoyed me.

Anyway, last month I bought a Parrot RKi8400 head unit, which promised much, but was ultimately the biggest pile of trash I've ever encountered, and I ended up returning it for a full refund. A2DP and handsfree both worked fine with my Pre- though.

I've replaced it with a Sony S300BTX, which is described as a "digital media receiver" and has a cute little tray to fit a USB hdd or an iPod into. Anyway, it supports bluetooth handsfree and A2DP streaming. The Pre connects to it fine, and the phone shows it's connected to it as an A2DP device (little music icon) and as a handsfree. The head unit shows both features connected perfectly too.

A2DP streaming works exactly as advertised, and all the phonebook functions work perfectly, but call audio is not reproduced by the head unit. The other party can hear me through the head unit's mic just fine, but I get no sound whatsoever.

I was running 1.4.5, and have just updated to 2.1 to see if that had any effect, but it's still no good - exactly the same problem. Sony do not list the Pre as being compatible (I checked this a touch too late I suspect), but support tells me this is because they've not tested it, not because it failed. I am reluctant to believe that it is simply not compatible, I find it hard to imagine that either Palm or Sony are doing something which is not entirely compliant with the bluetooth standards.

I highly doubt it's a problem with the Pre. My daughter has the Sony MEX-BT2700 which works perfectly with the Pre and others in the forum mention the Sony MEX-BT3800U works well too. It sounds more like the radio that's at fault.

Interesting comment, I've seen others using the 2700 or 3800 successfully on here too, and this was partly why I went for the Sony. I'm going to try an HTC Wildfire with it, and see if the same problem persists.